
The Holleford Crater - Hartington, Ontario Canada
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model12
N 44° 27.349 W 076° 37.672
18T E 370489 N 4923790
A meteor impact crater with a great view from the edge of the crater.
Waymark Code: WMBAMM
Location: Ontario, Canada
Date Posted: 04/26/2011
Views: 53
A meteorite traveling 55,000 kilometres per hour smashed into the earth here eons ago, blasting a hole 244 metres deep and 2.5 kilometres wide. Aerial photographs revealed the crater in 1955, and since then scientists have pieced together much of its geological history. Analyses of drill samples suggest that the meteorite struck in the late Precambrian or early Cambrian period (between 450 and 650 million years ago). At first the depression filled with water becoming a circular lake. Later Palaeozoic seas swept in sediments filling the crater to its present depth of about 30 metres. The explosive impact of the meteorite (estimated to have been only 90 metres in diameter) is still evident in the hundreds of metres of shattered rock that drilling has detected beneath the original crater floor.
In 1955, the Holleford meteor crater was discovered early in the systematic search of air photographs. The crater contains a thick layer of Palaeozoic sediments but still has the remnant of a rim, also mainly covered by sediments, rising 100 feet above the central region around approximately half the circumference. Beals (1960) has described the magnetic, seismic and gravity studies which preceded a diamond drilling program. The geophysical observations are well explained by the layers of sedimentary limestone above the lens of breccia which was revealed by the three drill holes sunk at varying distances from the centre. The identification of coesite in the drill core from Holleford and the microbrecciation of individual crystals revealed by microscopic studies (Bunch and Cohen 1963) demonstrate that strong shock effects were involved in the formation of this crater and support its identification as a meteorite crater.
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